Trimeric autotransporter adhesins (TAAs) are multimeric surface proteins, involved in various biological traits of pathogenic Gram-negative bacteria including adherence, biofilm formation, invasion, survival within eukaryotic cells, serum resistance and cytotoxicity.TAAs have a modular architecture composed by a conserved Mug membrane-anchored C-terminal domain and a variable number of stalk and head domains.In this study, a bioinformatic approach has been used to analyze the distribution and architecture of TAAs among Burkholderia cepacia complex (Bcc) genomes.Fifteen genomes were probed revealing a total of 74 encoding sequences.
Compared with other bacterial species, the Bcc genomes contain a disproportionately large number of TAAs (two genes to up to 8 genes, such as in B.cenocepacia).Phylogenetic analysis showed that the TAAs grouped into at least eight distinct clusters.TAAs with serine-rich repeats are clearly well separated from others, thereby representing a different evolutionary lineage.
Comparative gene mapping across Bcc genomes reveals that TAA genes are inserted within conserved synteny blocks.We further focused our analysis on the epidemic strain B.cenocepacia J2315 Ball - Umpire - Protective in which 7 TAAs were annotated.Among these, 3 TAA-encoding genes (BCAM019, BCAM0223 and BCAM0224) are organized into a cluster and are candidates for multifunctional virulence factors.
Here we review the current insights into the functional role of BCAM0224 as a model locus.